This invention pertains to a new class of yellow dye-forming couplers and to silver halide color photographic light-sensitive elements, emulsions and processes comprising such couplers. More specifically, the invention pertains to a new class of yellow couplers having a combination of a monocyclic or multicyclic carbon center attached to the 2-position of a substituted phenyl carbamoyl acetyl group and an aryloxy coupling-off group having a polarizable carbonyl, sulfonyl, sulfinyl, phosphonyl or phosphinyl moiety in the ortho position.
It is well known in the photographic art that color images are customarily obtained by a reaction between an oxidized aromatic primary amine developer and a color forming coupler. Typically, yellow dye-forming couplers are open chain ketomethylene compounds which yield azomethine dyes upon coupling with an oxidized developer. The most common yellow couplers are acylacetanilides, such as pivaloylacetanilides and benzoylacetanilides. Pivaloylacetanilide yellow couplers which are frequently used in the art have, in general, low coupling efficiencies due to their high pK.sub.a values. To overcome this problem, benzoylacetanilide couplers have been proposed and employed in the art. However, benzoylacetanilide yellow couplers yield image dyes with very poor light stability.
The foregoing classes of yellow couplers are described, for example, in U.S. Pat. Nos. 2,298,443; 2,407,210; 2,875,057; 3,048,194; 3,265,506; 3,447,928; 4,157,919; 4,230,851; 4,327,175; and 4,529,691, and in "Farbkuppler--ein Literaturubersicht," published in AGFA MITTEILUNGEN, Band III, pp. 112-126 (1961).
Although the aforementioned classes of yellow dye-forming couplers are frequently used in the photographic art, they nevertheless are still characterized by unsatisfactory coupling efficiency, image dye stability, solubility and dispersion stability. There has thus been a continuing search for novel couplers which improve upon existing couplers and optimize specific properties for particular applications. Among the photographically important properties, the coupling efficiency is of high interest. To enhance the coupling efficiency, 2-equivalent yellow couplers are disclosed and frequently used in the art. In particular, 2-equivalent yellow couplers having an aryloxy group as the coupling-off group have, in fact, attracted widespread attention. Yellow couplers having aryloxy coupling-off groups are disclosed, for example, in U.S. Pat. Nos. 3,408,194; 3,419,391; 3,429,391; 3,476,563; 3,644,498; 3,822,248; and 4,248,962.
U.S. Pat. No. 4,401,752 discloses that the coupling efficiency of pivaloylacetanilide-class yellow couplers can be improved with an aryloxy coupling-off group in which a polarizable carbonyl, sulfonyl or phosphonyl group is attached to the phenyl group at the ortho position.
One of the most effective of the many aryloxy coupling-off groups capable of enhancing the coupling efficiency of the pivaloylacetanilide-class yellow couplers is the sulfonyldiphenol (SDP) coupling-off group. The SDP coupling-off group affords superior coupling efficiency by virtue of the presence of the ionizable hydroxy group. However, while the SDP coupling-off group successfully enhances the coupling efficiency of the pivaloylacetanilide-class yellow couplers, it enhances coupling efficiency to a lesser extent when employed with two important new classes of yellow couplers, the 5-alkyl-1,3-dioxanoylacetanilide-class and the adamantoylacetanilide-class couplers, which are disclosed, for example, in U.S. Pat. Nos. 5,118,599 and 4,336,327.
There has thus been a continuing need for new coupling-off groups capable of enhancing the coupling efficiency of the dioxanyl- and adamantoylacetanilide-class yellow couplers.